OP here -> I'm going to put together some test apps - toss them on GitHub
and make sure I actually know what I'm talking about :)
On Friday, March 1, 2024 at 7:57:15 PM UTC-7 Ian Lance Taylor wrote:
> On Fri, Mar 1, 2024 at 6:17 PM Robert Engels <ren...@ix.netcom.com> wrote:
> >
> > The could be calling fork() as in the system call - which copies all
> file descriptors but I didn’t think Go processes could fork.
> >
> > Seems you would need to remap stdin and stdout in the fork to do
> anything useful.
> >
> > This sounds very PHP - what goes around comes around.
>
> Good point, I am assuming that the OP is using the os/exec package to
> start up a new copy of the process.
>
> A simple fork without an exec can't work in Go, or in any
> multi-threaded program.
>
> Ian
>
>
> > > On Mar 1, 2024, at 8:01 PM, Ian Lance Taylor <ia...@golang.org> wrote:
> > >
> > > On Fri, Mar 1, 2024 at 5:57 PM Jeff Stein <jeff...@gmail.com> wrote:
> > >>
> > >> I'm struggling to understand if I'm able to do something.
> > >>
> > >>
> > >> In my very odd use case we are writing a websever that handles
> connections via a forked process.
> > >>
> > >> I have a listener process that listens for TCP connections.
> > >>
> > >> So each net.Conn that comes in we pull off its file descriptor:
> > >>
> > >> fd, err := conn.(*net.TCPConn).File()
> > >>
> > >> duplicate that file descriptor and then fork off a process passing in
> that file descriptor.
> > >>
> > >> In my forked handler I'll reconstruct the HTTP connection and "do
> stuff".
> > >>
> > >> The concern I'm having is that it appears when I fork a process I
> inherit all of the parent file descriptors so if I have say 5 incoming
> connections and then I fork my child process technically could write to a
> different connection.
> > >>
> > >> I've played around with the various options:
> > >>
> > >> cmd.SysProcAttr = &syscall.SysProcAttr{Setpgid: false,}
> > >>
> > >> and using cmd.ExtraFiles
> > >>
> > >> No matter what I do I seem unable to limit the sub process to ONLY
> using the specific File Descriptor I want it to have access to.
> > >>
> > >> I believe this is doable in C - but I'm not sure if I can do this in
> GoLang as-is without mods .
> > >
> > > What you are describing shouldn't happen. A child process should only
> > > get the file descriptors explicitly passed via the os/exec.Cmd fields
> > > Stdin, Stdout, Stderr, and ExtraFiles. So tell us more: OS and
> > > version of Go, and what is showing you that all file descriptors are
> > > being passed down to the child.
> > >
> > > Ian
> > >
> > > --
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>
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